The present invention relates to an article comprising a water curable resin-coated sheet having a non-polar lubricant admixed with the resin coating which provides low tack for extended periods of time and to a method for preparation thereof. Although not so limited, the article of the invention has particular utility when produced in the form of tape material for preparing an orthopedic cast or bandage.
Prior art orthopedic casting tapes are available which comprise curable resin coatings on a substrate of fiberglass, polyester, or similar synthetic or natural fabrics. The use of water-curable urethane prepolymer for orthopedic tapes of this type is well known since water is a convenient medium for use in initiating curing of the resin prepolymer.
After curing of the prepolymer is initiated by contact with water, the resins become quite tacky until cured, thus causing difficulty in molding a cast around a body member. In order to avoid this problem, the prior art has disclosed the use of various materials to reduce the tack of resin coated tape or sheet material.
U.S. Pat. No. 3,089,486, issued May 1963 to Pike discloses the use of beeswax as a tack reducing agent in forming an orthopedic structure reinforced with a methacrylate polymer.
U.S. Pat. No. 3,630,194, issued Dec. 1971 to Boardman, discloses an orthopedic bandage comprising a flexible material supporting a solid vinyl monomer which is water curable. Inorganic fillers such as calcium sulfate, calcium carbonate, bentonite, or silica are added to reduce the tack and moderate temperature rise during curing.
U.S. Pat. No. 4,454,873, issued Jun. 1984 to Laufenberg et al, discloses an orthopedic bandage material having a thermoplastic resin and polyethylene oxide applied as an anti-block agent, the polyethylene oxide being in the form of a coating on the outer surface of the material or in the resin. Talc can also be added to reduce tack.
U.S. Pat. No. 4,667,661, issued May 1987 to Scholz et al, discloses a curable resin coated sheet useful as an orthopedic bandage, comprising a water-curable resin-coated sheet having a lubricant at the surface thereof, the lubricant being hydrophilic and present in an amount sufficient to reduce the kinetic coefficient of friction of the coated surface of the sheet material to less than about 1.2. The lubricant may be selected from a wide variety of materials which may be bound to the resin or added thereto, including sulfonate groups, a polyol, a polyethoxylated fatty alcohol, an alkyl sulfate surfactant, a polymer comprised of repeating units of ethylenically unsaturated monomers such as acrylamide, vinylpyrrolidone, vinyl acetate, etc., a polysiloxane, and polyethylene oxide groups. Preferably the resin is a water curable isocyanate-functional prepolymer.
U.S. Pat. No. 4,667,661 states that hydrophobic materials were initially evaluated as lubricants, but that such materials provided only a transient reduction in tack. More specifically, corn oil, mineral oil, hydrocarbons such as hexadecane and motor oil provided a non-tacky and slippery feeling surface, but on average the slippery effect lasted only a day to a week "apparently due to dissolution of the lubricant into the resin." In contrast to this, silicone based fluids reduced the tackiness of the resin without affecting other properties of the cast and remained on the surface of the resin even at elevated temperatures (Column 8, line 47 through line 2 of column 9).
Other patents relating to the use of additives in orthopedic wrappings or casts include U.S. Pat. Nos. 3,043,298; 3,763,858 and UK Patent Application 2,092,606.
Water-curable resins suitable for use in this field include polyurethanes, cyanoacrylate esters and the like, disclosed in U.S. Pat. Nos. 4,131,114; 4,411,262; and 4,502,479.
Despite the numerous disclosures in the prior art relating to the preparation of curable resin coated sheet or tape material for use as an orthopedic bandage or cast, there is still a definite need for such a product which has long shelf life, which utilizes an inexpensive, non-toxic lubricant for the reduction of tack and which can be prepared by simple mixing of the resin prepolymer and lubricant for application to sheet material.